Electrical Interfaces
AGD155 Product Manual Rev.2.2
Page 24
Safety Circuitry
Figure 12. Safety connector
Safety_Input_1 and Safety_Input_2 function independently, thus providing safety redundancy.
Each one can disable the power to the motor.
Both Safety_Input_1 and Safety_Input_2 disable the power to the motor through hardware
circuitry, without any software intervention.
Both Safety_Input_1 and Safety_Input_2 are defined with a positive pin (+) and a negative pin (-).
However, the opto-coupler at the Safety_Input has two input diodes, which enable operation at
"positive" or "negative" input voltage. The input is activated when current is sufficient at one of
the input diodes, regardless of the current direction. This enables NPN or PNP connection to the
safety inputs.
The Safety_Input protection logic is designed so that both Safety_Inputs must be powered to
enable motor operation. Leaving a Safety_Input disconnected prevents motor operation. This
logic is required to ensure that a disconnected safety cable is considered an unsafe condition by
the control unit. When sufficient current is driven through a Safety_Input, the state of this input
is
Safe
. When insufficient current is driven through a Safety_Input, the state of this input is
Unsafe
.
The two Safety_Inputs must be in the Safe state to enable motor operation.
Both Safety_Input_1 and Safety_Input_2, although acting on the drive hardware directly, are also
monitored by the controller software. The controller software generates a feedback signal to the
user (Safety_Feedback), which is also an isolated signal. This feedback is generated by the
software, and is activated if at least one of Safety_Input_1 or Safety_Input_2 signals is in the
Unsafe state.
The electrical characteristics of Safety_Input_1 and Safety_Input_2 are identical to those of all
other discrete, isolated inputs of the controller.
The safety inputs implemented in the product are currently pending certification Functional
Safety Standards.
